shelve: fix conversion of exceptions to strings flagged by pytype I've seen this done several ways and don't know what's correct. But pytype was unhappy about the previous way: FAILED: /mnt/c/Users/Matt/hg/tests/.pytype/pyi/mercurial/shelve.pyi /usr/bin/python3.6 -m pytype.single --imports_info /mnt/c/Users/Matt/hg/tests/.pytype/imports/mercurial.shelve.imports --module-name mercurial.shelve -V 3.6 -o /mnt/c/Users/Matt/hg/tests/.pytype/pyi/mercurial/shelve.pyi --analyze-annotated --nofail --quick /mnt/c/Users/Matt/hg/mercurial/shelve.py File "/mnt/c/Users/Matt/hg/mercurial/shelve.py", line 244, in _verifyandtransform: Function bytestr.__init__ was called with the wrong arguments [wrong-arg-types] Expected: (self, ints: Iterable[int]) Actually passed: (self, ints: Union[KeyError, TypeError, ValueError]) File "/mnt/c/Users/Matt/hg/mercurial/shelve.py", line 253, in _getversion: Function bytestr.__init__ was called with the wrong arguments [wrong-arg-types] Expected: (self, ints: Iterable[int]) Actually passed: (self, ints: ValueError) The following methods aren't implemented on ValueError: __iter__ Differential Revision: https://phab.mercurial-scm.org/D10122